This invention relates to touch screen input devices and, more particularly, to mechanical enhancements to touch screens.
Touch screen devices have become a commonplace user interface for electronic devices, computers, and the like. Touch screens are typically combined with a display screen which is in close proximity to the touch screen or which projects images through the touch screen. Under software control, the display may present images, video, alphanumeric information, and various combinations thereof. Moreover, the display may define corresponding areas of the touch screen as control input areas, through the presentation of control command words, iconic or graphic representations of controls, or the like. Thereafter, an operator touch at an appropriate portion of the touch screen causes the software to correlate the touch position with the control command defined by the display at that position, and to act on that command.
Touch screen sensor devices use many different operating principles, including infrared, capacitive sensor or resistive sensor techniques. Resistive sensor screens typically establish voltage gradients across orthogonal axes, and sense the touch point based on the voltage detected at a touch point as a ratio of the gradient. Capacitive sensor screens detect a signal input at a touch point, based on the capacitive coupling of a body through the tip of the finger impinging on the screen, or based on a signal transmitted from the tip of an input stylus. Some capacitive touch screens are designed to be placed behind a flat panel display, with a cover glass over the display. Others must be mounted over the top surface of a flat panel display. These latter devices may require touch sensing means on both the top and bottom surfaces of the touch screen, whereas others may require sensing means on only one surface, either front or back. Some touch sensor screens are capable of operation with a cover plate (superstrate) placed over the touch screen.
Touch screen technology is well adapted to eliciting operator inputs that are binary in nature: On/Off, Yes/No, Up/Down, Start/Stop, and like commands, that may be indicated with a single touch. There are other types of inputs, such as continuously variable values or functions, that many individuals prefer to control with real, palpable mechanical devices that permit a fine touch to be associated with a precisely selected level. For these inputs, a touch screen has not been well suited. Although a continuous gradient may be displayed as an image on a monitor or a flat panel display, and detected by a touch on a touch screen, it is necessary to slide the touch finger (or a stylus) along a graphic representation of a track or gradient that is displayed but lacks any physical structure or boundary. This action is difficult or awkward for many individuals, and requires that the user look at the displayed graphics in order to guide the controlling touch. In addition, many touch screens present an outer surface that is not well suited to sliding contact; e.g., the glass or plastic outer surface may lack sufficient lubricity.
The prior art reveals a lack of devices that may be used to make inputs to a system using a touch screen. On the other hand, the concept of combining electronic image display screens with operator input sensor apparatus correlated to the images presented on the display screen is well known in the prior art, as exemplified by the U.S. patents issued to the present inventor:    U.S. Pat. No. 5,572,239    U.S. Pat. No. 5,977,955    U.S. Pat. No. 5,805,146    U.S. Pat. No. 5,805,145    U.S. Pat. No. 5,936,613    U.S. Pat. No. 5,774,115